Adobe PHOTOSHOP 5.0 User Manual page 51

ON-SCREEN DISPLAY SIZE How large an image
appears on-screen depends on a combination of
factors––the pixel dimensions of the image, the
monitor size, and the monitor resolution setting.
The examples below show a 620 x 400 pixel image
displayed with various monitor sizes and monitor
resolutions.
13"
640 x 480
15"
832 x 624
20"
1024 x 768
640 x 480
640 x 480
Image resolution The number of pixels displayed
per unit of printed length in an image, usually
measured in pixels per inch (ppi). An image with
a high resolution contains more, and therefore
smaller, pixels than an image of the same printed
dimensions with a low resolution. For example,
a 1-inch-by-1-inch image with a resolution of
72 ppi contains a total of 5184 pixels (72 pixels
wide x 72 pixels high = 5184). The same 1-inch-
by-1-inch image with a resolution of 300 ppi
would contain a total of 90,000 pixels.
72-ppi and 300-ppi images; inset zoom 200%
Because they use more pixels to represent each
unit of area, higher-resolution images usually
reproduce more detail and subtler color transi-
tions than lower-resolution images when printed.
However, increasing the resolution of an image
scanned or created at a lower resolution only
spreads the original pixel information across a
greater number of pixels and rarely improves
image quality.
ADOBE PHOTOSHOP 5.0 43
User Guide